This invention relates to toilet systems that utilize a pressure differential to flush waste material from the toilet bowl to a waste-holding tank and in particular relates to such toilet systems in which the flushing liquid is not recirculated and which utilize fresh water for each flush to rinse the toilet bowl and assist in the evacuation of the waste matter from the bowl.
The use of differential pressure in municipal and domestic waste disposal systems is not of recent origin. The 1895 edition of Chambers' Encyclopedia describes a system in which the suction caused by pressure differential was used in place of water to remove waste material from a toilet bowl and move it to a waste holding or disposal tank. A vacuum flush system is especially desirable in situations where the use of water and gravity to flush waste from the bowl are restricted by the limited availability of large quantities of water for use in the flushing operation. Examples of situations in which water supplies are limited are in commercial passenger aircraft and other commercial conveyances, such as trains and boats, and also in vacation and resort dwellings that are located in remote areas with no municipal water system.
A vacuum flush toilet system for use in commercial aircraft is described in U.S. Pat. No. 3,995,328, issued Dec. 7, 1976 to Carolan et al. and assigned to the Assignee of the present invention, which is incorporated herein by reference. Previously, most toilet systems used in commercial aircraft have been of the recirculating type wherein the flushing liquid and waste material removed from the toilet bowl pass through a filtering system and the flushing liquid is recycled for use in later flushing of the toilet bowl. While recirculating flushing systems serve the purpose, it is desirable to make the toilet systems of commercial passenger aircraft as nearly as possible like those used by individuals in the home, so that the passenger will be more accustomed to the use of the system and feel more at ease. Also, recirculating toilets require a large-capacity filtration system in order to separate the flushing liquid from solid waste, thereby permitting the reuse of the flushing liquid. Such filtration systems require frequent maintenance and also present problems in odor control and sanitation.
The major drawback to the use of freshwater flushing in a commercial aircraft toilet system is the limited amount of water that can be dedicated to the flushing of toilet bowls. The most logical source of flushing liquid for the commercial aircraft is in the potable water supply, since each aircraft is generally equipped with such a potable water supply for each lavatory, however, use of the potable water supply for toilet flushing imposes a strict requirement that each flush use a minimum amount of water in order to conserve storage volume and minimize water weight in the aircraft. Also, to avoid complications in pressure regulation and valving, it is desirable that the pressure required of the flushing liquid be no higher than the potable water pressure so that the same valving and pressure-regulating equipment can be used for both the potable water and the flushing water.